Removal of Program to reinstall not gone entirely
To remove blender completely go to Control Panel -> Remove a program -> remove blender, then go to C:\Users\Your-Username\AppData\Roaming\ and remove the folder called Blender Foundation (This is where blender saves it's stuff), then reinstall blender.

about Blender 2.8, here is the link to download it: https://builder.blender.org/download/

just download the .zip folder, unzip it, then run the Blender.exe file (You don't need/have to "Install" it), Thats it :)